Electron tube amplifying system



May 24,1938. E. L. KOCH 5 ELECTRON TUBE AMPL'IFYING SYSTEM v Original Filed May 23, 1931 2 Sheets-Sheet l INPUT May 24,1938. E. L. KOCH 2,118,286v I ELECTRON TUBE AMPLIFYING SYSTEM Original Filed May 25, 1931 2 Sheets-Sheet 2 I aPZL 1 05/2.

Patented May 24, 1 938 PATENT OFFICE 2,118,286 ELECTRON TUBE AMPLIFYING SYSTEM Earl L. Koch, Chicago, Ill., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application May 23, 1931, Serial No. 539,468 Renewed September 29, 1936 19 Claims.

This invention relates to improvements in electron tube amplifying systems; and more I especially to a system of amplification for a radio receiver such as is used in radio broadcasting or radio telegraphy.

An object of the invention is to provide an amplifier system in which a thermionic tube serves as a coupling means between the input and. the output terminals of the amplifier system, both to aiford uni-directional conduction therethrough; and to adjust to a satisfactory value the potential impressed upon a grid or control electrode in said system. i

Another object of the invention is to provide an amplifier system having a thermionic tube of the three element type which is used as a coupling means for uni-directional conduotionbetween the input and the output terminals of the system, and which also serves as a rectifier for the high frequency oscillations impressed upon the amplifying system and utilizes only the negative half of each cycle for impressment upon a grid of the amplifier system to permit operation thereof with a normal grid bias of zero voltage.

A further object of the invention is to provide a resonant circuit in combination with suitable means associated with the output end of the amplifier system for changing the aforesaid unidirectional current into an alternating current of the same frequency as that impressed upon the input terminals of the amplifier system.

Yet another object of the invention is to provide an amplifier system in which a pair of vacuum tubes of the thermionic type are used as coupling means between the input and output endsof an amplifier system bothto adjust the voltage of a grid in the system and to permit unidirectional conduction between the said ends.

A still further object of the invention is to provide an amplifier system having a pair of thermionic tubes of. the three element type which are connected to assure uni-directional conduction between the input and output ends of the system, and which likewise rectify the incoming high frequency oscillations and give full-wave rectification thereof; but so arranged to allow as before a normal bias of zero voltage upon a grid when thesystem is in operation.

An additional object of the invention is to include means by which the resultant uni-directional current delivered by said pair of thermionic tubes is changed into a radio frequency current of a frequency double that of the original radio frequency impressed upon the input end of the amplifier, due to the full-wave rectification of the original impressed frequency by said thermionic tubes.

Other objects and advantages are set forth in the ensuing specification, taken with the accompanying drawings, showing some embodiments of ,1

the invention. The disclosure, however, is illustrative only, and changes in details may be made to the full extent consistent with the broad meanings of the terms of the appended claims, in which the novel features are more particularly pointed out.

On said drawings: Figure 1 shows a circuit diagram of an apparatus according to the invention; and

Figure 2 shows a similar circuit of another apparatus according to the invention.

The same numerals identify the same parts throughout.

Referring now more in detail to the invention as illustrated in Figure 1 of the accompanying drawings, the amplifier system is shown with an Input end and an Output end, which are so designated. The input end has associated with it one stage of amplification including an audion tube T comprising a filament 2, grid 3 and an anode or plate 4. A battery 6 and rheostat 5 associated with the filament 2 provides means for supplying current at the proper voltage; and a battery I connected through an inductance 8 to the plate 4 of the tube provides the necessary anode voltage. tube are an inductance 9 vand condenser ID in parallel forming a coupling circuit C tuned to the desired frequency.

A thermionic tube I l ofthe three element type including a filament l2, grid l3 and plate I4 is insertedin the'conductor l5 between the input end and the output end of the-amplifier, to serve as a coupling member to afford uni-directional conduction between the respective ends of the amplifier and as a rectifier to change the high frequency oscillations impressed upon the tube I l .into uni-directional current impulses. A battery I6 and rheostat I associated with the filament [2 of the thermionic tube l I give the revquired current for the filament l2.

The grid I3 is connected to ground l8 through a condenser l9; and a radio frequency choke 20 and battery 2| are associated with the grid l3. The plate M of the thermionic tube H is connected to the grid 22 of a three element tube T associated with a second stage of. amplification at the output end of the system. The filament 23 of the tube T is in series with the filament battery 26 and rheostat 25.

A battery 21 connected Across the output .circuitof. this to the plate 24 through an inductance 28 provides anode current for this tube. A second coupling circuit C including an inductance 29 and condenser 38 in multiple tuned to the operating frequency, is put across the output terminals of the system.

Radio frequency oscillations which are im' pressed upon the input end are amplified by the tube T and are impressed upon the filament I2 of the thermionic tube II. The filament I2 being heated by the battery I 6, an electron flow is established between the filament I2 and the plate I4. When the positive half of a cycle of the amplified radio frequency oscillations is impressed upon the filament I2 of the tube I I, the filament becomes positive with respect to the plate I4 of the tube II, and then the flow of electrons from the filament I2 to the plate I4 ceases; but when the negative half of the cycle is impressed upon the filament I2 of the tube II, the filament I2 becomes more highly negative with respect to the plate I4, to permit electron flow from the filament I2 to the plate I4. The path thus formed in the tube II completes a circuit for an active current to fiow from the plate I4 to the filament I2, through the inductance 9, and the resistance 35 connected as shown, and back to the plate I4. This current will be uni-directional and will be impressed upon the grid 22 of the tube T; making the voltage of this grid vary between zero and some negative value. Hence the thermionic tube II in addition to forming a coupling member to conduct uni-directional current between the ends of the amplifier system, acts as rectifying means, utilizing only the negative half of each cycle of the radio frequency oscillations impressed upon the grid of the first tube T. The tube T and the circuit C containing the inductance 28 and condenser 38 associated with the output end of the amplifier changes the uni-directional current to an alternating current of a frequency which is the same as that which is impressed upon the input end of the amplifier.

The grid I3 of the thermionic tube II is connected to ground I8 through the condenser I9; and the choke coil 21! in series with the biasing battery ZI, which has its negative lead connected to one terminal of the filament I2 and its other positive terminal connected to the grid I3 of the tube II through said choke coil 2!], maintains the grid I 3 sufficiently positive to reduce the space charge and the impedance of the tube.

Referring now in detail to the invention as presented inFigure 2, the amplifier system is shown with a pair of coupling and rectifier tubes. As before, the input end has associated with it one stage of amplification comprising an audion tube T with the same connections and tuned coupling circuit C; and the output end of the amplifier systeznhas the second stage of amplification including the audion tube T with the same connections as before, and circuit C. Between the tubes T and T are the thermionic tubes II and II, which effect full-wave rectification of the impressed radio frequency oscillations at the input end of the amplifier. These tubes II and II comprise filaments I2, grids I3, and plates I4, with rheostats I1 and batteries I 6 for the filaments, and batteries 2| and radio frequency choke coils 20 between the grids and filaments. The grids of the respective tubes II and II are connected to ground 32 through the respective condensers I9 and I9, the common terminal of which is connected to the midpoint of the inductance 9.

The radio frequency oscillations arriving at the input end and amplified in the stage of amplification including the tube T, inductance 8, and coupling circuit C, are impressed upon the filaments I2 of the thermionic tubes II and II. The filaments I2 being connected to either end of the inductance 9, when the positive half of a cycle of the amplified radio frequency oscillation is impressed upon one of the filaments I2 that filament I2, upon which a positive potential is applied, will be positive with respect to its associated plate I4 and thus prevent any electron movement toward the plate so that'no current can flow through one of the tubes II and II. When the negative alternation of a cycle is alternately applied, the filaments of the tubes I I and II will alternately become quite negative with respect to the adjacent plates I4 to permit an electron flow and thus an active current will be set up. The tubes II and II will be alternately operative during successive half cycles of the amplified radio frequency oscillations, thus utilizing all the energy of the cycleand producing full-wave rectification of the radio frequency oscillations. The plates I4 are in parallel; and with the connections as shown in Figure 2, a uni-directional cur rent is generated only as the filaments alternately become negative, this current always traversing the resistance 35 in the same direction. The grid 22 of the tube T thus normally has a zero voltage, when no high frequency oscillations are flowing through the rectifiers, and'a voltage varying between zero and some negative value when oscillations are caused to flow through said rectifiers.

The batteries 2I again are biasing batteries which have their negative terminals connected to the filaments I2 of the tubes II and II and their positive terminals connected via the chokes 20 to the grids I3 to maintain the grids I3 sufficiently positive to reduce the space charge and the tube impedance.

The stage of amplification associated with the output end of the amplifier system acts as a resonant circuit to change the full-wave rectified current delivered by the tubes II and II into oscillations of frequency double the frequency of the oscillations that were originally impressed upon the input end of the amplifier, due to the full rectification of the original impressed frequency. Hence this arrangement serves as a frequency doubler in addition to giving all the results obtained by the circuits shown in Figure 1.

Suitable condensers may be placed in the output leads of the anodes 4 and 24, between these and the circuits C and 0.

What is claimed is:

1. Radio apparatus comprising thermionic amplifying tubes in cascade, said tubes each containing a cathode, a grid, and an anode, and a three-element rectifier between said tubes, said rectifier having a cathode, a: grid and an anode, the cathode of the rectifier being connected to the output of one of the amplifying tubes, the grid of the rectifier being capacitively connected to the cathodes of said amplifying tubes, and the anode of the rectifier to the input of the other amplifying tube, thereby rectifying high frequency oscillating currents supplied to one of said amplifier tubes into uni-directional current.

2. Radio apparatus as claimed in claim 1, in which the output side of each of said amplifying tubes has a tunable coupling circuit associated therewith.

3. Radio apparatus comprising an amplifying member, a rectifier comprising a cathode and an anode with a grid member interposed therebetween, said grid member being electrically grounded through a by-pass condenser, means for impressing a high frequency electrical oscillating current input to said cathode and said grid member to be converted into unidirectional current by said rectifier, and connections from the anode and grid of said rectifier to said amplifying member including a shunt input resistance between said anode and a control element of the amplifying member, and ground potential to maintain the control element of the input of the latter at zero potential when no high frequency current is applied to said rectifier and to impress upon said amplifying member control element negative half cycles when high frequency current is applied to said rectifier. v

4.'Radio apparatusc'omprisin'g an amplifying tube having a grid, a cathode and an anode, a pair of vacuum tube rectifiers, each containing a cathode, an anode and a grid between said cathode and anode acting as a radio frequency shield therebetween whereby current flowing between said cathode and anode is solely due to thermionic conduction, said rectifiers having their inputs connected in phase opposition with their cathodes disposed across an input circuit to receive electrical oscillations, said apparatus containing a common load circuit for uni-directional current from said rectifiers, and connections from said load circuit to the grid and cathode of the amplifying tube whereby the latter may deliver through its anode said oscillations in amplified and augmented form.

5. Radio apparatus comprising means for producing successive stages of amplification, with an amplifying vacuum tube associated with each of said stages, tuning means associated with the output circuits of each of said tubes and a pair of vacuum tube rectifiers, each containing a cathode, an anode and a grid comprising a radio frequency shield therebetween for controlling the thermionic conduction therein, said grids being electrically grounded for alternating current through by-pass condensers, said rectifiers having their inputs connected in phase opposition and connected between said amplifying tubes, the cathodes of the rectifiers being connected to the output circuit of one of said amplifying tubes, the grids being connected to a midpoint in the tuning means associated with said output circuit and the anodes to the input circuit of the other amplifying tube for delivering to an input element of the latter uni-directional current from both of said rectifiers.

6. In a radio amplifying system, an amplifying tube, a pair of half wave vacuum tube rectifiers, each containing a cathode and an anode with a grid positioned therebetween, circuits between the output of said amplifying tube and said cathodes comprising the input of said rectifiers whereby the latter may receive electrical oscillations from said amplifying tube, a second amplifying tube having its control element connected in circuit with the anodes of said rectifiers whereby said control element may receive full wave high frequency uni-directional current from said rectifiers acting conjointly, 'means capacitively associating the grids of said rectifiers with grouhd potential, and a shunt circuit connected between the control element of said last amplifying tube and ground potential, said last circuit including a resistance adapted to maintain the grid of the last amplifying tube at a negative bias when the rectifier is delivering current thereto and at zero bias when no current is passing through the rectifiers.

7. Radio apparatus according to claim 3 in which the cathode of the rectifier is normally maintained at a negative bias and the grid of the rectifier is maintained at a positive bias.

8. Radio apparatus comprising means for producing successive stages of amplification, with an amplifying vacuum tube having input and output circuits associated with each of said stages, a pair of thermionic vacuum tube rectifiers with inputs connected in phase opposition, each rectifier having a cathode, an anode and a grid therebetween for the purpose of electrostatically shielding said cathode from said anode, adapted to cause the conduction between said elements to be uni-directional and thermionic in nature; blocking condensers connected between said grids and ground potential, connections between the output circuit of one of said amplifying tubes andthe cathodes of said rectifiers, connections between the anodes of said rectifier and the input circuit of a second of said amplifying tubes, means including a shunt load resistance connected to said-last input circuit for maintaining the control element of said second amplifying tube at zero potential when no high frequency current is applied to said rectifier, said shunt load resistance also being connected to form a common load circuit for said rectifier whereby, when high frequency current is applied to said rectifier, negative impulses only will flow in said shunt load resistance with the result that only negative unidirectional impulses are applied to the control element of said second amplifying tube.

9. In radio apparatus comprising means for producing successive stages of amplification, an amplifying tube having input and output terminals, a three-element thermionic rectifier having a cathode, a grid and an anode, connections between the output terminal of said first tube and the cathode of said rectifier, a second amplifying tube, connections between the anode of said rectifier and a control element of said last amplifyingtube, a capacitor connected between the grid of said rectifier and ground potential, a circuit including resistance connected between said control element of said second amplifying tube and ground potential, said last circuit being adapted to maintain the control element with which it is associated at zero potential when no high frequency current is being applied to said rectifier, and to maintain said last'control element at negative potential when rectified negative half cycles from the rectifier are impressed thereon.

10. In an amplifying circuit, an amplifying tube, a rectifier, means for impressing high frequency signal currents upon said rectifier tobe converted into uni-directional currents, a direct connection from said rectifier to said amplifying tube to produce amplified uni-directional currents in the output circuit of said amplifying tube, and means for converting the amplified uni-directional currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

11. In an amplifying circuit, an amplifying tube, a rectifier, means for impressing high frequency signal currents upon said rectifier to convert the same into uni-directional currents, a di rect connection from said rectifier to said amplifying tube to produce amplified uni-directional currents in the output of said amplifying tube, and means comprising a resonant circuit tuned to the frequency of said signal currents connected in the output circuit of said amplifying tube for converting the amplified uni-directional currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

12. In an amplifying circuit, an input circuit, a linear rectifier, connections from said circuit for impressing high frequency signal currents upon said rectifier to convert the same into unidirectional currents, an amplifying tube, a direct coupling connection from said rectifier to the input of said amplifying tube to produce amplified uni-directional signal currents in the output circuit of said tube, and means for converting the amplified uni-directional signal currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

13. In an amplifying system, an input circuit, a diode rectifier, a direct coupling connection from said input circuit to said rectifier for impressing high frequency signal currents upon said rectifier to convert the same into uni-directional currents, an amplifying tube, a direct coupling connection from said rectifier to said amplifying tube to produce amplified uni-directional currents in the output circuit of said tube, and means for converting the amplified uni-directional currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

14. In an amplifying system, an input circuit, a rectifier having a cathode, anode and a grid intermediate said cathode and said anode, means for maintaining said grid at a positive potential relative to said cathode, connections from said input circuit to said rectifier for impressing high frequency signal currents upon said rectifier to convert the same into uni-directional currents, an amplifying tube, a direct coupling connection from said rectifier to said amplifying tube to produce amplified uni-directional currents in the output circuit of said tube, and means comprising a resonant circuit tuned to the frequency of said signal for converting the amplified uni-directional currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

15. In an amplifying system, a resonant input circuit, a diode rectifier having a cathode and an anode, load impedance means in series with said rectifier connections from said input circuit to said rectifier for impressing high frequency sig nal current upon said rectifier to convert the same into uni-directional currents, an amplifying tube, a direct coupling connection from the junction point between said rectifier and said impedance to said amplifying tube to produce amplified uni-directional currents in the output circuit of said tube, and means including a resonant circuit tuned to the same frequency to which said input circuit is tuned, connected in the output circuit of said amplifying tube for converting the amplified uni-directional signal currents into alternating currents having a frequency which is the same as the frequency of said signal currents.

16. In an amplifying system, a resonant input circuit, a diode rectifier having a cathode and an anode, a resistance element, said resonant circuit, said rectifier and said resistance element being connected to form a circuit whereby high frequency input signals impressed upon said resonant circuit are converted into uni-directional currents, an amplifier having a cathode, a grid and an anode, connections from said resistance to the grid and cathode of said amplifier whereby the grid of said amplifier is at cathode potential when no high frequency current is applied to said rectifier and whereby the negative half cycles of a high frequency current are impressed upon the grid of said amplifier when a high frequency signal is impressed upon said input circuit, and means for converting the amplified uni-directional currentsin the outputof said amplifier into oscillating currents having a frequency equal to said input signals.

17. In a system as claimed in claim 15 in which said rectifier includes a grid electrode intermediate its cathode and anode, and means for maintaining said grid at a positive potential relative to said cathode.

18. A method of amplifying high frequency signals which consists in rectifying the signals to produce uni-directional currents, amplifying the uni-directional currents by direct current amplification and reconverting the amplified unidirectional currents into oscillating currents of the original signal frequency.

19. A method of amplifying high frequency signals which consists in linearly rectifying the signals to produce uni-directional signal currents, amplifying the uni-directional currents by direct current amplification and converting the amplified uni-directional currents into oscillating currents of the original signal frequency.

EARL L. KOCH. 

